Linux gets all the copy these days, so it's easy to forget that its origins lie in the Unix operating system, and Unix is still very much alive and kicking, even among companies embracing Linux. IBM has AIX, Sun/Oracle has Solaris, and HP has HP-UX.

HP-UX still plays a major role at HP, powering its Itanium-based Integrity servers that are used in the most vital of mission-critical environments. Recently, HP issued another update to the OS to bring it up to date with new technologies like virtualization and cloud computing. ServerWatch dives into the new version.

Sun's UNIX ecosystem was thrown into turmoil following the company's acquisition by Oracle. A big question mark remains over the future of Solaris and OpenSolaris server operating systems. In contrast, IBM and HP, the other two big enterprise UNIX players, have been plodding along steadily, hoping all the while to pick up disaffected Sun customers quicker than they lose their own to Linux implementations.

Let's focus on HP (NYSE: HPQ). Linux leaves the company in a rather tricky situation. That's because HP is a big fan of the open source server software -- it's a phenomenon too big to ignore. But it also sells UNIX, so it has to be careful not to cannibalize its UNIX sales by promoting Linux too hard. In other words, HP's UNIX and Linux staff must push their respective lines of business without unduly dissing their opposite numbers.